The invention relates to the field of electronics. In particular, the invention deals with a one-shot circuit.
The monostable multivibrator or one-shot is a circuit that produces a pulse of a certain duration, in response to an input pulse or trigger. One way of producing a pulse of desired duration, is through the use of a delay line that provides a fixed time delay. For instance, an input trigger can be fed directly into one of the inputs of an AND gate, and into the other input of the AND gate via a delay line that includes an inverter (e.g., an odd number of inverters).
The delay elements in such a circuit, are, however, subject to the same process variations as other components on a semiconductor chip, which can significantly influence the integrity of the output pulse.
The present invention seeks to provide a more flexible solution in which the duration of the output pulse of the one-shot need not be predecfined and fixed at the time of manufacture, and can take account of process variations.
The invention involves a new one-shot circuit which provides for multi-faceted programmable pulse width control, wherein at least one of the programming method comprises multiple selectable delay lines, while another takes the form of a programmable counter. The multiple selectable delay lines may be connected to each other through transmission gates selectable by a decoder for selecting one of multiple of delay lines. There may be more than one set of selectable delay lines. The circuit typically has a plurality of feedback loops, and each feedback loop may be provided with a set of selectable delay lines. The one-shot is typically implemented as at least two flip-flops, and a programmable counter/comparator.
According to the invention, there is provided a one-shot circuit comprising at least a first and a second flip-flop wherein the output of the first flip-flop is coupled to an input of the second flip-flop, and further comprising a counter coupled to the output of the second flip-flop, the output of the counter is coupled to the clear pins of those flip-flops. The circuit typically includes a first feedback loop with an inverter from an output of the second flip-flop to a clock input of the second flip-flop, and a second feedback loop from an output of the second flip-flop to a clear input of the second flip-flop. The feedback loop from the output of the second flip-flop to the input of the second flip-flop preferably includes a first programmable delay line. The feedback loop from the output of the second flip-flop to the clear input of the second flip-flop may include a second programmable delay line. The counter provides a direct adjustment for the period of the output pulse for the one-shot circuit. The second flip-flop with its feedback loops from its output to its clock and clear inputs defines an internal clock, and the programmable delay lines provide adjustments for the period of the internal clock signal.
Further, according to the invention, there is provided a one-shot circuit comprising at least a first flip-flop, a second flip-flop defining an internal clock, and a counter, wherein the internal clock causes the counter to count up and the counter serves to reset the first flip-flop once the counter has reached the value set by the program value. The circuit further comprises a first flip-flop coupled to an input of the second flip-flop. Preferably the counter is also coupled to a clear pin of the second flip-flop.